They defiantly took as their symbol the pink triangle that Hitler's henchmen had made people like them wear. They declared "Silence = Death." They took to the streets with loud voices and a white-hot anger. And they saved lives, and changed history.

"How to Survive a Plague" -- opening Friday (Oct. 19) for a weeklong run at the Zeitgeist Multi-Disciplinary Arts Center -- is their story, the story of ACT UP and other gay activists, and how, at a time when AIDS was misunderstood and mostly ignored, they stood up, and fought back.

They didn't just fight the disease, though -- forming their own education and social-care groups, writing policy papers on clinical-trial protocols, even importing foreign drugs that had shown promise. They also fought everyone -- politicians, scientists, the Catholic Church -- they saw as standing in their way.

"How to Survive a Plague" is, apart from a lovely score, roughly made. The chronology isn't always clear, and its focus on New York can be parochial. (There's barely a mention of San Francisco, and not one word about Randy Shilts' epic history "And the Band Played On.") Yet it's an undeniably powerful film.

Of course, few things are more thrilling in cinema than seeing an underdog fight back -- and few groups have been more marginalized than gays, many kept secret and silent for years by their own, very real fears. But when a health crisis hit in the `80s, and the defiantly all-uppercase ACT UP picked up steam, they were heard. (And -- with a decidedly large contingent of writers, artists, actors and filmmakers -- what they said and did was often memorable).

Yet apart from the thrill of seeing everyone from shy teenagers to anguished mothers stand up, the film also sadly shows how the disease ravaged those it struck and how, for so many years, a diagnosis was the same as a death sentence.

And so we see walking skeletons, all eyes and cheekbones and rough purple lesions, crying for justice. Too many eulogies given. And, in a scene from a Greek tragedy, furious relatives marching on Washington, and hurling the cremains of their loved ones onto the White House lawn.

There is some humor -- as when, incensed by Sen. Jesse Helms' constant attacks, they cover his home in a giant canvas "condom." (ACT UP always knew the value of street theater -- and, unlike the Occupy movement -- the power of a few, very clear-cut demands.)

But mostly the film toggles between two emotions: the high of watching brave people go to war, and the low of seeing so many of them fall, as entire communities are destroyed. ("Will the last person alive in Chelsea," one man bitterly jokes, "please turn off the lights?")

It's tempting to focus only on the film's positive message: that people can make a real difference in the world. The men and women in this film educated themselves, and educated others, and as a result money was raised, research pushed forward, and drugs rushed to the market. Millions of lives were saved.

And yet you can't watch the film without thinking about the millions of lives that were needlessly lost, as politicians either downplayed the pandemic or demonized its victims. And wonder how many more millions of lives continue to be needlessly lost, around the world.

Note: Director David France will participate in a live Q-and-A via Skype after the 7:15 p.m. screening on Saturday(Oct. 20). Newhouse News Service movie critic Stephen Whitty wrote this review.

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HOW TO SURVIVE A PLAGUE4 stars, out of 5

Snapshot: A documentary about the birth of the gay-rights movement, and its rise to power.

What works: It is undeniably powerful stuff.

What doesn't: It's also rough-around-the-edges stuff, with a chronology that isn't always clear and a focus on New York that borders on the parochial.